Capacitor having tapered cylindrical storage node and method for manufacturing the same

ABSTRACT

A capacitor is made by forming a buffer oxide layer, an etching stop layer, and a mold insulation layer over a semiconductor substrate having a storage node contact plug. The mold insulation layer and the etching stop layer are etched to form a hole in an upper portion of the storage node contact plug. A tapering layer is deposited over the mold insulation layer including the hole. The tapering layer and the buffer oxide layer are etched back so that the tapering layer is remained only at the upper end portion of the etched hole. A metal storage node layer formed on the etched hole over the remaining tapering layer. The mold insulation layer and the remaining tapering layer are removed to form a cylindrical storage node having a tapered upper end. A dielectric layer and a plate node are formed over the storage node.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean patent applicationnumber 10-2006-0138476 filed on Dec. 29, 2006, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a method for manufacturing capacitor ofa semiconductor device, and more particularly to a capacitor having atapered cylindrical storage node to prevent leaning of the cylindricalstorage node and a method for manufacturing the same.

As the semiconductor memory devices such as DRAMs are highly integrated,the width of a capacitor, which serves as a storage for storing data inthe memory device, is narrower. The capacitor is made of a dielectriclayer interposed between a storage node and a plate node, and thecapacitance is proportional to the surface area of the node and adielectric constant of the dielectric layer and inversely proportionalto a distance between the nodes, i.e. a thickness of the dielectriclayer.

Accordingly, in order to obtain a capacitor of high capacity, it isrequired to use a dielectric layer having a large dielectric constant,and/or to enlarge the surface area of the node, and/or to reduce adistant between the nodes. However, limitations exist as to the extentthe distant between the nodes, i.e. a thickness of the dielectric layer,can be reduced, and as such the studies were focused on finding ways ofusing a dielectric layer having a large dielectric constant or enlargingthe surface area of the node to form a high capacity capacitor.

A typical method for enlarging the surface area of the node includes amethod of forming a three dimensional storage node having a concave orcylindrical shape. The cylindrical shape storage node is considered moreadvantageous to realize a capacitor of high capacity than a concave typestorage node, because it has larger node area.

However, although not shown and described in detail, a dip-out processfor removing a mold insulation layer is carried out in order to form thecylindrical storage node and, during a drying procedure in the dip-outprocess, a storage node could lean to cause bridging of two adjacentstorage nodes due to the surface tension of deionized water (DIW) andthe increased height of the storage node.

Accordingly, as a way to ensure and prevent the leaning of the storagenode and the bridging between the adjacent storage nodes, it wasrequired to secure the cell-to-cell spacing of more than the desireddistance and to reduce the height of the storage nodes.

However, since the spacing between cells is already narrow from the maskstate due to the reduction of design rule to achieve high integration ofsemiconductor devices, it is difficult to ensure the adequatecell-to-cell spacing using a conventional etching process and acylindrical storage node forming process, and thus it is impossible toprevent the leaning of the cylindrical storage node. Consequently, it isimpossible to form stably a cylindrical capacitor when it is made in aconventional way as described above.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a capacitor inwhich a leaning of a cylindrical storage node is prevented and a methodfor manufacturing the same.

Further, embodiments of the present invention are directed to acapacitor capable of realizing stably a cylindrical capacitor bypreventing generation of a bridge between adjacent storage nodes due tothe leaning of a cylindrical storage node and a method for manufacturingthe same.

In one embodiment, a capacitor may comprise a semiconductor substrateprovided with a storage node contact plug; a cylindrical storage nodeformed over the semiconductor substrate so as to be in contact with thestorage node contact plug, an upper end portion thereof having a taperedshape; a dielectric layer formed over the cylindrical storage node; anda plate node formed over the dielectric layer.

The capacitor may further comprise a metal silicide layer formed at aninterface between the storage node contact plug and the cylindricalstorage node.

The metal silicide layer is preferably a TiSi_(x) layer.

The storage node is a metal layer made of at least one of TiN, WN, TaN,Ru, and Pt.

The dielectric layer is one of a ZrO₂ layer, an Al₂O₃ layer, and alaminated layer of Al₂O₃ layer and ZrO₂ layer.

The plate node is a metal layer made of at least one TiN, WN, TaN, Ruand Pt.

In another embodiment, a method for manufacturing a capacitor maycomprise forming a buffer oxide layer, an etching stop layer, and a moldinsulation layer over a semiconductor substrate provided with a storagenode contact plug; etching the mold insulation layer and the etchingstop layer to form a first hole in an upper portion of the storage nodecontact plug; depositing a tapering layer over the mold insulation layerincluding the first hole, a thickness of the tapering layer at an upperend portion being thicker that that at a lower end portion; etching backthe tapering layer and the buffer oxide layer so that a second hole forexposing the storage node contact plug is formed and the tapering layeris remained only at an upper end portion of the second hole; forming ametal layer for a storage node at a surface of the second hole includingthe remaining tapering layer; removing the mold insulation layer and theremaining tapering layer to form a cylindrical storage node, an upperend portion thereof having a tapered shape; and forming a dielectriclayer and a plate node over the storage node.

The etching stop layer is a nitride layer.

The mold insulation layer is a single layer of PE-TEOS or a double layerof PSG layer and PE-TEOS layer.

The tapering layer is formed as an oxide layer of one of a PE-TEOSlayer, a PE-USG layer, an O₃-USG layer, a LP-TEOS layer, a HTO layer,and a SiON layer.

The tapering layer is deposited according to a CVD or PECVD process to athickness of 50 to 500 Å at an upper end portion of the first hole andto a thickness of 10 to 100 Å at the lower end portion of the firsthole.

The tapering layer remaining at an upper end portion of the second holehas a thickness of 20 to 100 Å.

The method may further comprise forming a metal silicide layer,preferably a TiSi_(x) layer, over the storage node contact plug, afteretching back the tapering layer and the buffer oxide layer but beforeforming the metal layer for the storage node.

The storage node is formed as a metal layer made of at least one of TiN,WN, TaN, Ru, and Pt according to a CVD or ALD process.

The dielectric layer is formed as one of a ZrO₂ layer, an Al₂O₃ layer,and a laminated layer of Al₂O₃ layer and ZrO₂ layer, and the Al₂O₃ layerand the ZrO₂ layer are formed using Zr[N(CH₃)]₂, Zr[N(CH₂CH₃)]₂, orZr[N(CH₃)(CH₂CH₃)]₂ as a source of Zr, using Al(Ch₃)₃ as a source of Al,and using O₃ or H₂O as a source of O according to an ALD process at atemperature of 200 to 480° C.

The plate node is formed a metal layer made of at least one TiN, WN,TaN, Ru, and Pt. Preferably, the plate node is a TiN layer formed as adouble layer according to the CVD and PVD processes or a double layeraccording to the ALD and PVD processes.

In the other embodiment, a method for manufacturing a capacitor maycomprise forming a buffer oxide layer, an etching stop layer, and a moldinsulation layer over a semiconductor substrate provided with a storagenode contact plug; etching the mold insulation layer, the etching stoplayer, and the buffer oxide layer to form a hole for exposing thestorage node contact plug; depositing a tapering layer over the moldinsulation layer including inside the hole, wherein the thickness of thetapering layer at an upper end portion is thicker that than thethickness of the tapering layer at a lower end portion; etching back thetapering layer to expose the storage node contact plug, wherein thetapering layer is remained only at an upper end portion of the hole;forming a metal layer for a storage node on the surface of the holeincluding the remaining tapering layer at an upper end portion of thehole; removing the mold insulation layer and the remaining taperinglayer to form a cylindrical storage node, wherein an upper end portionof the cylindrical storage node has a tapered shape; and forming adielectric layer and a plate node over the storage node.

The tapering layer is formed in a CVD or PECVD process.

The tapering layer is deposited to a thickness of 50 to 500 Å at anupper end portion of the hole and to a thickness of 10 to 100 Å at alower end portion of the hole.

The tapering layer remaining at an upper end portion of the hole has athickness of 20 to 100 Å.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a capacitor in accordancewith an embodiment of the present invention.

FIGS. 2A through 2G are cross-sectional views illustrating the processsteps of a method for manufacturing the capacitor in accordance with anembodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a capacitor in accordancewith an another embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

A preferred embodiment of the present invention is directed to acapacitor, in which an upper end portion of a cylindrical storage nodeis formed to have a tapered shape. By doing this, since a cell-to-cellspacing, that is a space between the cylindrical storage nodes isensured, a leaning of the cylindrical storage node and the resultantgeneration of a bridge between adjacent storage nodes can be prevented.

Hereafter, an embodiment of the present invention will be described withreference to the attached drawings.

FIG. 1 is a cross-sectional view illustrating a capacitor in accordancewith an embodiment of the present invention. As shown, the capacitor 160in accordance with an embodiment of the present invention includes astorage node 152, a dielectric layer 154, and a plate node 156, andparticularly the storage node 152 has a cylindrical structure in whichits upper end portion is tapered.

In this case, in relation to the shape of the storage node 152 in whichits upper end portion is tapered, the space between the adjacentcylindrical storage nodes is increased when compared to the conventionalstructure, and thus an adequate cell-to-cell spacing is ensured.Accordingly, in accordance with an embodiment of the present invention,a leaning of the cylindrical storage node as well as the resultantgeneration of a bridge between the adjacent storage nodes can beprevented through ensuring the adequate cell-to-cell spacing.

Therefore, in accordance with an embodiment of the present invention,the production yield can be increased since formation of cylindricalcapacitors can be stably carried out, and a semiconductor memory deviceof high capacity can also realized through the formation of thecylindrical capacitor.

In FIG. 1, the reference numeral 110 indicates an interlayer insulationlayer, 112 indicates a storage node contact plug, 114 indicates a bufferoxide layer, 116 indicates an etching stop layer, 142 indicates aTiSi_(x) layer and H2 indicates a hole for the storage node.

FIGS. 2A through 2G are cross-sectional views illustrating the processsteps of a method for manufacturing the capacitor in accordance with anembodiment of the present invention and the description to this is asfollows.

Referring to FIG. 2A, after the interlayer insulation layer 110 isformed over an upper portion of the semiconductor substrate 100 formedwith a base structure (not shown) including a transistor, the storagenode contact plug 112 made of polysilicon is formed in a desired placein the interlayer insulation layer 110. Over the interlayer insulationlayer 110 including the storage node contact plug 112, the buffer oxidelayer 114, the etching stop layer 116, and a mold insulation layer 120are sequentially formed.

The etching stop layer 116 is preferably formed of a nitride layer, andthe mold insulation layer 120 is preferably formed of a double layer ofa PSG layer 122 and a PE-TEOS layer 124. It may be possible to form themold insulation layer 120 as a single layer of PE-TEOS.

An amorphous carbon layer is formed as a hard mask material over themold insulation layer 120. After that, a hard mask 130 is formed bypatterning the amorphous carbon layer through a photolithography processand etching process to expose a portion of the mold insulation layer 120in a storage formation area, which corresponds to an upper area of thestorage node contact plug 112.

Referring to FIG. 2B, the mold insulation layer 120 and the etching stoplayer 116 are etched using the hard mask 130 as an etching mask untilthe buffer oxide layer 114 is exposed, thereby forming a first hole H₁.At this time, most of the thickness of the hard mask 130 is removed, andthus only some thickness is remained. A tapering layer 140 is depositedover the hard mask 130 including the first hole H₁.

The tapering layer 140 is an element for causing the upper end portionof the cylindrical storage node to be formed to a tapered shape and isdeposited with a non conformal deposition property that a depositionthickness at an upper end portion of the first hole H₁ is thicker thanthat at a lower end portion. For example, the tapering layer 140 isdeposited with an oxide layer of one of PE-TEOS layer, PE-USG layer,O₃-USG layer, LP-TEOS layer, HTO layer, and SiON layer according to aCVD or PECVD process and is deposited to a thickness of approximately 50to 500 Å at the upper end portion of the first hole H₁ and a thicknessof approximately 10 to 100 Å at the lower end portion of the first holeH₁.

Referring to FIG. 2C, by etching the tapering layer 140 and the bufferoxide layer 114 through an etch back process, a portion of the taperinglayer 140 formed over the mold insulation layer 120 and the remaininghard mask 130 below the portion of the tapering layer 140 are removed,and at the same time a second hole H₂ for exposing the storage nodecontact plug 112 is formed. At this time, the tapering layer 140 remainsat or near the upper end portion of the second hole H₂, and thethickness of the remaining tapering layer 140 is preferablyapproximately 20 to 100 Å.

Referring to FIG. 2D, in order to decrease the contact resistancebetween the storage node contact plug 112 made of polysilicon and ametal storage node to be formed subsequently, a metal silicide layer142, for example a TiSi_(x) layer, is formed at the interfacetherebetween. The TiSi_(x) layer is formed by depositing a Ti layer overthe second hole H₂ including the remaining tapering layer 140 and themold insulation layer 120 and then by carrying out a rapid heattreatment. Over the second hole H₂ including the silicide layer 142 andthe mold insulation layer 120, a metal layer 150 for storage node isformed. The metal layer 150 for storage node is formed of one or more ofTiN, WN, TaN, Ru, and Pt according to a CVD or ALD process. Preferably,the metal layer 150 for storage node is formed of TiN.

Referring to FIG. 2E, a portion of the metal layer 150 for storage nodeformed over the mold insulation layer 120 is removed according to aknown process so that the adjacent storage nodes are separated from eachother.

Referring to FIG. 2F, the mold insulation layer 120 is removed through adip-out process to form the cylindrical storage node 152. When the moldinsulation layer is removed, the remained tapering layer 140 is alsoremoved through a cleaning process in the dip-out process.

Herein, since the cylindrical storage node 152 of the present inventionhas a shape that its upper end portion is slightly bent inward by thetapering layer 140 (as shown removed in FIG. 2F), the space between theadjacent cylindrical storage nodes 152, i.e. the cell-to-cell spacing,is increased. Therefore, the cylindrical storage node 152 is restrictedfrom leaning during a dip-out process of the mold insulation layer 120,and thus the bridging between the adjacent cylindrical storage nodes 152is prevented.

Therefore, the production yield is increased as the present inventionprovides stable and reliable ways of forming cylindrical capacitors, andfurther as the cylindrical storage nodes formed according to the presentinvention have a larger aspect ratio than the conventional products, thepresent invention provides superior ways to realize high capacitysemiconductor memory devices.

Referring to FIG. 2G, the dielectric layer 154 and the plate node 156are sequentially formed over the etching stop layer 116 including thecylindrical storage node 152, thereby completing formation of acylindrical capacitor 160 in accordance with an embodiment of thepresent invention. The dielectric layer 154 is formed of a ZrO₂ layer,and the thickness thereof is approximately 30 to 150 Å. It may bepossible to form the dielectric layer 154 as an Al₂O₃ layer or a doublelayer of Al₂O₃ layer and ZrO₂ layer. The ZrO₂ layer and Al₂O₃ layer areformed using Zr[N(CH₃)]₂, Zr[N(CH₂CH₃)]₂, or Zr[N(CH₃)(CH₂CH₃)]₂ as asource of Zr, and using Al(Ch₃)₃ as a source of Al, and using O₃ or H₂Oas a source of O according to an ALD process at a temperature of 200 to480° C. The plate node 156 is a metal layer made of one or more of TiN,WN, TaN, Ru, and Pt. Preferably, the plate node 156 is formed of the TiNlayer, and the TiN layer is formed as a double layer according to theCVD and PVD processes or a double layer according to the ALD and PVDprocesses.

As is apparent from the above description, in an embodiment of thepresent invention, since the cylindrical storage node 152 is formedusing the tapering layer 140 to a shape in which its upper end portionof the cylindrical storage node 152 is inwardly tapered, the spacebetween the adjacent storage nodes 152 is increased, thereby preventingthe leaning of the cylindrical storage node and the bridging of twoleaning adjacent storage nodes. Therefore, the production yield isincreased due to reliable formation of the cylindrical capacitors.

Also, in an embodiment of the present invention, since the upper endportion of the cylindrical storage node is formed to an inwardly taperedshape, the cylindrical storage nodes having a larger aspect ratio largerthan the conventional products can be formed, and thus the capacitancecan be increased to realize a memory semiconductor device of highcapacity.

FIG. 3 is a cross-sectional view illustrating a capacitor in accordancewith another embodiment of the present invention. According to the thisembodiment, a tapering layer 140 is performed after forming a third holeH₃ for exposing a storage node contact plug 112 by etching a moldinsulation layer 120, etching stop layer 116 and a buffer oxide layer114.

In that outside, the remaining manufacturing process is identical with apreviously execution embodiment, the detailed description in order toomit.

Although the specific embodiments of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and the spirit of theinvention as disclosed in the accompanying claims.

1. A capacitor, comprising: a semiconductor substrate provided with astorage node contact plug; a cylindrical storage node formed over thesemiconductor substrate so as to be in contact with the storage nodecontact plug, an upper end portion of the cylindrical storage nodehaving a tapered shape such that the upper end portion of the storagenode is bent inward so as to increase cell-to-cell spacing; a dielectriclayer formed over the cylindrical storage node; and a plate node formedover the dielectric layer.
 2. The capacitor according to claim 1,further comprising a metal silicide layer formed at an interface betweenthe storage node contact plug and the cylindrical storage node.
 3. Thecapacitor according to claim 2, wherein the metal silicide layer is aTiSi_(x) layer.
 4. The capacitor according to claim 1, wherein thestorage node is a metal layer made of at least one of TiN, WN, TaN, Ru,and Pt.
 5. The capacitor according to claim 1, wherein the dielectriclayer is one of a ZrO₂ layer, an Al₂O₃ layer, and a laminated layer ofAl₂O₃ layer and ZrO₂ layer.
 6. The capacitor according to claim 1,wherein the plate node is a metal layer made of at least one of TiN, WN,TaN, Ru, and Pt.